Coated granular explosive composition



;number of difierent causes. effect of moisture which becomes ofparticular Patented Oct. 28, 1952 UNITE :ooA'rEn GRANULAR EXPLOSIVECOMPOSITION Charles D..Goodale, Terre Haute, Ind., assignor toCommercial Solvents Corporation, ,Terre Haute, Ind, acorporation ofMaryland No Drawing. Application April 27, 1948, Serial No. 23,622

1 2 Claims.

1 This'invention relates to-explosive compositions containingwater-soluble or hydroscopic com- :pounds. More particularly, it relatesto ammonium nitrate compositions of reduced hydro- -scopicity an'd watersolubility, and to processes of importance in case the explosive or oneof its ingredients is either water soluble or hydroscopic as is the casewith ammonium nitrate, explosives .;of the dynamite type, black powder,etc. Ammoinium nitrate in particular is a very extensively usedingredient in present day high explosives of the dynamite type where ithas replaced nitroglycerine inincreasinglylarge proportions for avariety of reasons-particularly because it possesses 'high'explosivestrength, has outstanding safety properties,:an'd is economicallyattractive. While ammonium nitrate explosives have been used with greatsuccess, one disadvantage of this ingredient has always been evident,namely, that it has great aflinity for water. Because of this fact,there is a tendency for explosive compositions high in ammonium nitrateto become hard and set on storage in the presence of even small amountsof moisture. This results in decreased sensitivity of the explosive anda lesser degree of uniformity in performance. The water resistance ofammonium nitrate explosives is generally low because of the presence ofthis very soluble salt.

Numerous attempts have been made in the past to reduce the efiects ofmoisture on explosives afiected thereby. Altho many attempts which havebeen made in the past to reduce the effect of moisture on explosives ofthe above type the efforts have most commonly been directed towardscoating the individual particles of the explosive with somewaterproofing or water-repellent material such as waxes, celluloseesters, resins, oils, soaps, sodium silicate, and the like. None ofthese materials has been entirely successful for various reasons. Insome cases complete coverage of the particles has not been obtained, inothers the coating material is affected 'bysome other constituent of theexplosive, and

instill others the coating material has had an undesirable effect uponthe explosives by either slowingup or reducing the power oftheexplosive.

I have now discovered that water-soluble or *hydroscopic explosives canbe satisfactorily pro- .tected from :the effect ofmoisture without thedisadvantages ofthe materials previously tried :forthis purposetbycoatingthe particles of the explosives or the constituents thereof whichare affected. by water with-the compound 2,2-dinitropropane. highlyefiective in protecting the ammoniumni- 'trate, Or other explosives, .oringredients of the explosives, 'fromtheefiectsof moisture possesses Thismaterial, iii addition ,to being the highly important property of notmaterially affecting the explosive characteristics of the materialswhich have been treated with it. It

has a sensitivity comparable with that of-trivnitrotoluene and doesnotexplode in=five seconds .at a'temperature of 360 C. and in'300minutes :at 135.C.. The ballistic power of 2,2-dinitropropane is 123 (T.N. T.=), and while it can be detonated it is relativelystable. Whenignited, it burns with a moderately-vigorous'fiame. These properties,therefore, make .-2,2-dinitropropane ideallysuited fortreating: ammoniumnitrate or :other water-soluble 0r hydroscopic explosives,

making it resistant to the action of moisture.

The 2,2-dinitropropane can be applied to the ammonium nitrate, or otherexplosives, or ingredients of explosives, in a number of ways withequally satisfactory results and it is understood that I am limited tono particular procedure. Suitable methods which may be mentioned includecoating the material to be protected with molten 2,2-dinitropropane (M.P. 50-53 C.), or with a suitable solution thereof, the latter procedurebeing, in general, both more economical and more easily effected.

The 2,2-dinitropropane is readily soluble in such solvents as methanol,ethanol, acetone, methyl ethyl ketone, ethyl acetate, ethyl ether,dioxane, methyl ether of ethylene glycol, nitromethane, Z-nitropropane,benzene, ethylene chloride, acetic acid, and the like, and is somewhatsoluble in cyclohexane, ethanol amine, and ethyl ene glycol, but onlyvery slightly soluble in water, caustic solution, petroleum ether, andn-heptane.

The particular method of applying the 2,2-dinitropropane in accordancewith my invention selected will depend on a number of factors such asthe character and cost of the explosive to be treated, the availabilityand cost of the soldirectly poured over the crystals. In any case,

after contacting the crystals in a solution of 2,2-dinitropropane it is,of course, necessary to remove the solvent by some suitable means such 1as evaporation, preferably in the manner so as to recover the solventused. The removal of the solvent then leaves a coating of2,2-dinitro-propane on the erystals,'the amount of 2,2-dinitropropanecoating depending upon the concentration of the solution of.2,2-dinitropro-pane employed.

The concentration of -2,2-dinitropropane used in my process will,ofcourse, depend upon the solubility in the particular solvent selected,the method of coating'ernployed, andthe .thickness of coating desirednonthe crystals. While the latter may vary rather widely, it is in. generaldesired to use a solution of sufficient concentration to give a coatingamounting from about 0.1% to about5'.0% by weight of the dry ammoniumnitrate or other explosives. The lower limit is determinedby the degreeof moisture protection desired and the effectiveness of the coatingmaterial Wher'eas the upper limit is determined 'by the eifect of the2,2-dinitropropane upon the particular material beingcoated, andthe'relative costs of the -2,2dinitropropane. and the material beingcoated. Because of the explosive characteristics of 2,2-dinitropropanethese-latter factors are in general more importantthan in the case withmaterials previously, used as ingredients of coatings because of thedeleterious effects of these prior art materials on the explosives.

The protective action of 2,2-dinitropropane may be prolonged by using itin combination with moderate amounts-of materials serving to retard thevolatility of the 2,2-dinitropropane, such as, for example,high-boiling, relatively non-volatile liquids, like butyl stearate anddibutyl phthalate or low-melting resins such as rosin and beeswax, Anyvolatility retarder of such types may be employed providedit iscompatible with the 2,2-dinitropropane in the amount used, which ispreferably within the range of 5% to based on the weight of the2,2-dinitropropane.

Now having described my invention, what I claim and desire to protect byLetters Patent is:

1. A hydroscopic, Water-soluble explosive in granular form coated with amixture comprising at least about 0.1% by Weight of 2,2-dinitropropanebased on the weight of said explosive and from about 5 to 30% of ahigh-boiling, relatively non-volatile liquid, based on the weight ofsaid 2,2-dinitropropane, said liquid being inert to and compatible withsaid 2,2-dinitropropane.

2.- Ammonium nitrate in granular form coated with'a mixture comprisingatleastabout 0.1% by weight of 2,2-dinitropropane based on the Weight ofsaid ammonium nitrateand from about 5 to 30% of a, high-boiling,relatively non-volatile liquid, based on the weight of said2,2-dinitropropane, said liquid being inert to and compatible with said2,2-dinitropropane.

, CHARLES D. GOODAIE.

REFERENCES CITED The following references are of reco'rd in the file ofthis patent:

UNITED STATES PATENT OTHER. REFERENCES I Hass et al., TheNitroparaffinsj Chem.

. Reviews, vol. 32, pp. 386-388, June 1943,

1. A HYDROSCOPIC, WATER-SOLUBLE EXPLOSIVE IN GRANULAR FORM COATED WITH AMIXTURE COMPRISING AT LEAST ABOUT 0.1% BY WEIGHT OF 2,2-DINITROPROPANEBASED ON THE WEIGHT OF SAID EXPLOSIVE AND FROM ABOT 5 TO 30% OF AHIGH-BOILING, RELATIVELY NON-VOLATILE LIQUID, BASE ON THE WEIGHT OF SAID2,2-DINITROPROPANE, SAID LIQUID BEING INERT TO AND COMPATIBLE WITH SAID2,2-DINITROPROPANE.